RE: how much k/e ?
Two years ago I shot a rig that produced 56 ft lbs of KE Leaving the bow. I shot a deer at 14 yards right through the heart. I got a pass through. That same year I shot a deer at 28 yards right through the heart. I did not get a pass through. The heart offered enough resistance to stop the arrow on the longer shot. That was using an 1 1/4 inch mechanical broadhead.
what I want is as much as I can get with the draw weight I can live with.
Broadhead size makes a difference also. A large broadhead offers more resistance than a smaller one. Arrrow weight makes a difference also.
So it depends on what your using, how far, and what you hit.
No cut and dry answear for your question.